Digital communications methods are methods that send digital information (encoded in bits, 0 or 1) instead of sending an analog signal, such as voice or video.

The methods listed here are all digital modes:

• Packet Radio is probably the best known digital mode which can be thought of as using a modem over a radio to allow computers to exchange data

• JT65 is a digital protocol developed for amateur radio communication with extremely weak signals. It was designed by Joe Taylor, K1JT, to optimize Earth-Moon-Earth (EME) contacts on the VHF bands. The "65" refers to the 65 tones the protocol uses.

• PSK31 is short for Phase Shift Keying, 31 Baud and is more of system for chat over radio; it allows realtime keyboard to keyboard informal chat between operators.

• MFSK is short for Multiple frequency-shift keying and is a variation of FSK, a method used by some packet radio systems.

• IEEE 802.11 is a set of specifications for implementing wireless local area network (WLAN) computer communication in the 900 MHz and 2.4, 3.6, 5, and 60 GHz frequency bands.

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APRS, Automatic Packet Reporting System, is a standard utilizing packet radio and a GPS to send beacons with the location of the unit. There are many things you can do with APRS, but many use it on bicycles to track their progress, on their vehicle to track where it is, etc. There have even been reports of APRS- equipped vehicles being stolen and then quickly tracked down thanks to the APRS unit.

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Automatic location reports need to know the location to automatically report; thus, they use a GPS just like anything else would =]

If you think about this one, it couldn't be the speedometer anyway; that would only tell you how fast you are going. (also APRS, Automatic Position Reporting System, can be used when biking, driving, walking, etc all just as easily as the other). The other two options are just random things thrown in hoping you won't know what they are so you'll guess wrong. Nearly everyone knows what a GPS is, so this shouldn't be hard to remember.

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NTSC is the name of the standard used to encode colors in an analog fast scan color TV signal.

If you ask a broadcast engineer, NTSC stands for Never The Same Color, because his job is to keep all the cameras looking the same. Now that TV is in the Digital Age the only people you see using the NTSC broadcast standard are Amateur Radio Operators.

Actually, NTSC stands for National Television Systems Committee. They created the rules that governed what the broadcast signal would be electronically so every TV would be able to display the correct picture

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It helps to know what APRS is and does. First, APRS stands for Automatic Packet Reporting System. It transmits a station's GPS coordinates, so other stations can locate it. The components are a GPS receiver, a ham radio transmitter, and some logic to connect the two so the transmitter sends out the GPS coordinates. So:

It has nothing to do with counting packets, It doesn't require voice over Internet, and It doesn't count stations connected to a repeater.

It just provides real time communications that gives your location. In conjunction with a map, it shows your location to the stations that receive your GPS coordinates via the APRS system.

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Phase Shift Keying is a method for digitally transmitting data (with a computer of some sort) by varying (keying) the phase of the signal.

Phase refers to where you are in the cycle -- the peaks and valleys of the sine wave.

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DMR (Digital Mobile Radio) is one of several digital modes. It's the only one that uses time-multiplexing to allow two digital voice signals to be repeated through the same repeater, using the same 12.5 kHz repeater channel.

It's not a position tracking system.

It's not a logging technique.

The third distractor is tempting, because it talks about two simultaneous repeater inputs, but the part about time-multiplexing is unique to DMR, so the best answer.

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A checksum is an error detection method used by many data transmission types including packet radio. Basically all bytes in the message are added (summed) up and sent as a "checksum". The receiving station repeates this process and "checks" the result against the checksum it received from the sending station.

If the checksum fails (the sums don't match) then an automatic repeat request is sent.

Since packet radio is a form of amateur radio communications the destination station is generally identified at least by call sign, so that information is often included in the header as well.

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CW stands for "Continuous Wave", which is a sine wave: an electromagnetic wave of constant amplitude and frequency.

This wave can be interrupted, creating an "off" state. The on and off states can be used to transmit Morse code.

The original version of Morse code developed by Samuel Morse is often referred to as Railroad Morse code or American Morse code—American because the rest of the world adopted International Morse. Eventually International Morse also replaced Railroad Morse in America, and this is what we use today.

The term CW comes up a lot; whether you remember what CW stands for or not, every amateur radio operator should know that CW means Morse code.

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WSJT [Weak Signal JT(after the program's initial author, Joseph Hooton Taylor Jr.)] is software that facilitates short, quick digital transmissions and is very useful for weak signals.

As such, it's great for moonbounce (Earth-Moon-Earth), weak signal beacons and meteor scatter, all of which result in very little of the transmitted signal reaching anyone's receiver.

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ARQ stands for Automatic Repeat reQuest

When the receiving station detects an error, it automatically sends a repeat request to the sending station.

It has nothing to do with encryption (which would be illegal except for sending commands to a satellite), or video signals, or data compression.

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Broadband-Hamnet™ was at one time called HSMM-Mesh™ and is one of a couple of different projects which are basically intended to create a peer to peer wireless network on ham radio frequencies.

The first iteration of this involved using the Linksys WRT-54G -- a highly modifiable consumer access point -- with custom firmware on 2.4ghz channel 1, which is actually part of the ham radio allotted spectrum. The idea is that "mesh nodes" can connect to each other automatically and route traffic between each other, thus providing a wireless network which covers a city (or larger) by creating interlinking nodes.

In practice this is more difficult than you might expect, due to congestion on 2.4ghz frequencies, but the project has expanded to include support for other access points and bands as well. There are some offshoots of the project, including AREDN (Amateur Radio Emergency Data Network) and HamWan.

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FT8 is a relatively new digital mode which became popular in 2017. FT8 stands for Franke-Taylor 8-Frequency-Shift Keying modulation. FT8 was created by Joe Taylor, K1JT, and Steve Franke, K9AN.

It very quickly largely replaced JT65 because it's much faster. FT8 is usually used on HF bands and it can achieve very long distances because it is extremely tolerant of noise and interference. It requires that both transmitter and receivers synchronize their computer time with the same time source (which is easy with the internet).

When you transmit, you transmit for 15 seconds and send only a very short (75 bit) message with a 12 bit checksum. Hint: Remember FT as fifteen.

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An electronic keyer is the modern fancy replacement for the traditional telegraph key, or in other words a device that assists in manual sending of Morse code.

Electronic keyers can have a variety of functions including:

• Separate keys for sending dots and dashes at a specified rate.
• The ability to set a limited transmission rate (in WPM) while allowing the operator to "get ahead" of the current transmission by buffering up additional code or word spaces to be sent in sequence after previously entered code is sent.
• The ability to continually send dots or dashes by holding down a key so that fewer hand movements are required to transmit a series of dots or dashes.
• The ability to combine some functions with the use of a traditional key that is plugged into the electronic keyer.

Often they are hardware devices but they can also be computer or smartphone software applications that provide these and other functions.

Electronic keyers.... They just might save you from carpal tunnel syndrome!

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